Protein 14-3-3 Influences the Response of the Cardiac Sodium Channel Na(v)1.5 to Antiarrhythmic Drugs.

The cardiac sodium channel Na(v)1.5 is a key contributor to the cardiac action potential, and dysregulations in Na(v)1.5 can lead to cardiac arrhythmias. Na(v)1.5 is a target of numerous antiarrhythmic drugs (AADs). Previous studies identified the protein 14-3-3 as a regulator of Na(v)1.5 biophysical coupling. Inhibition of 14-3-3 can remove the Na(v)1.5 functional coupling and has been shown to inhibit the dominant-negative effect of Brugada syndrome mutations. However, it is unknown whether the coupling regulation is involved with AADs' modulation of Na(v)1.5. Indeed, AADs could reveal important structural and functional information about Na(v)1.5 coupling. Here, we investigated the modulation of Na(v)1.5 by four classic AADs, quinidine, lidocaine, mexiletine, and flecainide, in the presence of 14-3-3 inhibition. The experiments were carried out by high-throughput patch-clamp experiments in an HEK293 Na(v)1.5 stable cell line. We found that 14-3-3 inhibition can enhance acute block by quinidine, whereas the block by other drugs was not affected. We also saw changes in the use- and dose-dependency of quinidine, lidocaine, and mexiletine when inhibiting 14-3-3. Inhibiting 14-3-3 also shifted the channel activation toward hyperpolarized voltages in the presence of the four drugs studied and slowed the recovery of inactivation in the presence of quinidine. Our results demonstrated that the protein 14-3-3 and Na(v)1.5 coupling could impact the effects of AADs. Therefore, 14-3-3 and Na(v)1.5 coupling are new mechanisms to consider in the development of drugs targeting Na(v)1.5. SIGNIFICANCE STATEMENT: The cardiac sodium channel Na(v)1.5 is a target of commonly used antiarrhythmic drugs, and Na(v)1.5 function is regulated by the protein 14-3-3. The present study demonstrated that the regulation of Na(v)1.5 by 14-3-3 influences Na(v)1.5's response to antiarrhythmic drugs. This study provides detailed information about how 14-3-3 differentially regulated Na(v)1.5 functions under the influence of different drug subtypes. These findings will guide future molecular studies investigating Na(v)1.5 and antiarrhythmic drugs outcomes.